1. Field of the Invention
The present invention relates to a communication method, a communication system, a communication terminal and a communication managing apparatus suitable for application to communication utilizing a radio communication terminals such as a portable telephone, mobile telephone, a portable information terminal or the like.
2. Background of the Invention
In a radio communication system using a radio communication terminal such as a portable radiophone, a mobile telephone, a portable information terminal or the like, each of the communication terminals carries out communication with a base station prepared on the side of communication network so as to connect to the communication network through the base station, whereby the communication terminal carries out communication with a desired opponent.
In this case, every communication terminal utilized in the communication system has set therein an identification number (so-called ID data) as an identical number of each terminal. Further, a communication managing center controlling the communication with the respective communication terminals has stored therein identification numbers of all communication terminals. The identification numbers are numbers exclusively useful for control in the communication network, and hence the identification numbers are, in general, not open to the public. Thus, the identification numbers are different from so-called telephone numbers.
The communication managing center for controlling communication with the respective communication terminals compares an identification number transmitted from each of the communication terminals and an identification number stored in the communication managing center with each other when the base station carries out communication with each of the communication terminals. If the identification numbers agree with each other, the communication managing center determines that the corresponding communication terminal is recognized, and carries out authentication processing for starting the communication.
FIG. 1 shows one example of an arrangement of a conventional communication system in which authentication processing is required. This communication system is a radiophone system in which an arbitrary number of a mobile station 1 as a communication terminal (in this case, portable telephone sets) is connected, wherein each of the mobile stations 1 carries out radio communication with a base station 2. The communication system includes a plurality of base stations 2 and a service area is formed depending on locations of the base stations 2. Each of the base stations 2 is connected to a telephone network 3, and each mobile station 1 can be connected through the base station 2 and an exchanger 301 within the telephone network 3 to an arbitrary telephone 4 of a subscriber. In some cases, each mobile station may be connected through the exchanger 3 by way of another base station 2 of the network to another mobile station (not shown).
In the mobile station 1 as the communication terminal, a transmission and reception circuit 102 carries out processings of transmission and reception under the control of a control unit 101 which is formed of a microcomputer so as to serve as a system controller. The transmission and reception circuit 102 is connected with an antenna 103 and a signal processed by the transmission and reception unit 102 is transmitted from the antenna 103 to the base station 2 side in a wireless fashion. Also, a signal transmitted from the base station 2 side is received by the antenna 103 and subjected to a reception processing in the transmission and reception unit 102.
A communication speech signal extracted from the signal received by the transmission and reception unit 102 is supplied to a handset 104 so that a speaker provided in the handset 104 emanates a sound. Further, a speech signal picked up by a microphone provided in the handset 104 is subjected to a transmission processing in the transmission and reception circuit 102 to transmit the processed speech signal to the base station 2 side through the antenna 103.
In the base station 2, a transmission and reception circuit 202 carries out transmission processing and reception processing under control of a control unit 201 provided for controlling communication. Specifically, a signal is transmitted from an antenna 203 connected to the transmission and reception circuit 202 in a wireless fashion and a radio signal received by the antenna 203 is subjected to reception processing in the transmission and reception circuit 202.
When a communication speech signal is transmitted between the mobile station 1 and the base station 2, in addition to the communication speech signal, a control signal is transmitted therebetween. That is, when communication is started by calling from either of the mobile station 1 and the base station 2, a control signal useful for calling a callee is initially transmitted. Before communication is started, control signals are transmitted bidirectionally so that the base station 2 side carries out authentication processing with its control unit 201 about the mobile station 1. Only when it is confirmed that the mobile station is an authentic terminal, control is carried out to start the communication between the mobile station 1 and the base station 2. This communication control is carried out by communication between the control unit 201 in the base station 2 side and the control unit 101 in the mobile station 1 side. In order to carry out the authentication processing, the mobile station 1 side has a fixed ID memory unit 105 and an ID comparing unit 106 so that the control unit 101 carries out the authentication processing by using the fixed ID memory unit 105 and the ID comparing unit 106. Also, on the base station 2 side, a fixed ID memory unit 302 and an ID comparing unit 303 are supplied in a communication managing center provided in the communication network 3 and that the base station 2 side can carry out the authentication processing by using the fixed ID memory unit 302 and the ID comparing unit 303. The fixed ID memory unit 105 in the mobile station 1 has stored therein identification data (hereinafter referred to as a fixed ID) set in advance for its own station. The fixed ID memory unit 302 in the communication network 3 has stored therein fixed IDs for all mobile stations capable of connecting to the communication system.
Now, the conventional authentication processing carried out by the system arrangement of FIG. 1 will be described.
In this case a description will be given of an example in which the mobile station 1 is called by calling a telephone 4 of a general subscriber. Initially, when a dial of the telephone 4 of the general subscriber is operated, a telephone number of a particular mobile station 1 is discriminated by the exchanger 301. Then, a telephone line is connected to a base station 2 located in an area in which the mobile station 1 is present. Thereafter, the control unit 201 in the base station 2 carries out calling processing for the corresponding mobile station 1. At this time, the control unit 201 reads out the fixed ID of the mobile station 1 from the fixed ID memory unit 302 and transmits a command directing that the mobile station 1 is to send back its fixed ID. The mobile station 1 reads out its own fixed ID stored in the fixed ID memory unit 105 and transmits the same to the base station 2 in accordance with the command.
The comparing unit 303 compares an ID read out from the fixed ID memory unit 302 in the telephone network 3 side with the ID transmitted from the mobile station 1, and the base station 2 determines by its control unit 201 whether they are coincident with each other or not. If it is determined that they are coincident to each other, then it is determined that the authenticity of the terminal is confirmed. Thereafter, a communication channel between the telephone of the general subscriber and the mobile station 1 and so on are set so that a speech signal or the like can be transmitted through the channel. Thus, communication is started.
Further, when a telephone call is made from the mobile station 1, operation upon the receiving call as described above is carried out inversely. That is, the mobile station 1 compares by its ID comparing unit 106 an ID transmitted from the base station 2 side with the ID set for its own station so as to carry out authentication processing (alternatively, the base station side may carry out the authentication processing by the comparing operation even when the mobile station makes a calling).
In this manner, the authentication processing is carried out for the opponent with which communication is made. Thus, it is possible to call a particular terminal designated by a telephone number or the like and make the particular terminal to be connected network, and also it is possible to prevent a non-registered terminal from being utilized as a mobile station illegally.
In the conventional system, however, the ID of each mobile station is a fixed code data. Therefore, if the ID is once discriminated by any method, a terminal authentically not registered can be utilized as a mobile station illegally by using the ID. Particularly, when the communication system is a radiophone system, the charge for a telephone call is imposed on an owner of an authenticated terminal using the same ID. Therefore, the charge for the illegal telephone call may be imposed on the authenticated user.